I commented to clarify the question, but since "toning" up the shoulders is physiologically impossible unless you plan to lose body fat, I'll give some exercises that have worked for me in the past in terms of getting bigger and stronger delts.
First, absolutely nothing beats an overhead press when it comes to building shoulders (proven both by EMGs and years of experience), and since you're already doing these, fantastic!
Second, in terms of pure isolation, there are a few options here for each head of the shoulder...I'll give my favorites.
When it comes to shoulder isolation work, one thing that many people don't seem to be aware of is that, your hand position actually matters quite a lot as seen from numerous studies. What I mean by this is for example, it's been found that when you do dumbbell front raises, you get the most activity from your front deltoids when your hand position is neutral (palms facing your body like a hammer curl) as opposed to palms down or up. With that in mind, a very simple but very effective isolation exercise for front delts is obviously just front raises. As opposed to most, I actually don't recommend doing these with dumbbells, since most of the other shoulder movements are done using dumbbells, you want to introduce some new stimulus. Instead, grab a weight, 25-45lbs will do, grab it like a steering wheel, with your arms basically fully straight, and do a front raise to VERY slightly above parallel your shoulders (NOT MUCH or you risk impingement) and squeeze your front delts. This is works a lot of core as well and you can handle more weight with a plate as opposed to a dumbbell so all the better. As another twist on these, you can do them with cables obviously or just plain dumbbells if you feel them better. Also, I know this may seem weird but it's been found through EMG scans and just my personal experience, that pec dec (the chest fly machine) actually works your front delts to a great extent, if you want to add that in occasionally. As an additional tip, on top of overhead press, if you incorporate some push presses into your shoulder routine, you will work all three heads of your shoulders to a great extent, you won't really need more than 1-2 isolations after this. Also builds great power and helps you get "toned" if your diet is right, since they burn a lot of calories and release hormones (just look at olympic lifters and their shoulders).
In terms of side delts, there's only two primary isolation movements that are well accepted and have been studied. Lateral side raises and upright rows. There's no need to complicate things here, if you want to isolate your side delts do side raises. To get the most out of these grab lower on the dumbbell, i.e get your pinkies higher than your first 3 fingers, almost like you're pointing your elbows up but not much. You can also do these with cables to change things up. Just make sure you focus on lifting with your elbows and not wrists. You can also do upright rows but I don't recommend it since these put you in a very good position to get injured and they're not really worth it in my opinion. That's more or less it for side delts, note these also work rear delts to a good degree.
In terms of rear delts, a very good exercise is just a reverse pec-dec (if your gym has this machine), it's pretty straight forward how to do this, so I'm sure you know how to do it pretty well anyways. Another good variation is seated reverse flies. To do these, sit at the edge of a bench, grab a pair of dumbbells, your palms can either face you or they can face back (it's been shown that more rear delts are activated in the latter while more side delts are activated in the previous), slightly bend over (don't round your lower back too much or at all if possible) so that you're upper body is about 45 degrees or a bit lower to the ground, and do the same motion as the reverse pec dec, i.e do a reverse chest fly, LEADING WITH THE ELBOWS, with arms as straight as possible but not fully straight. Note that also, in shoulder exercises the arms are kept straight only to spare the biceps of extra strain, so keeping them mostly straight with a slight bend is fine.
Additionally, these aren't isolation movements but shrugs and rows and pullups work the side and rear delts to quite some degree as I'm sure you're aware.
As a final note, I want to point out that while isolation work for shoulders is great, you obviously know (I'm assuming since you have a high rep) compound movements (since muscle growth happens on a systematic level in natural lifters i.e from big movements) and a caloric surplus with adequate protein are the first two necessary things for shoulder and muscle growth in general. Isolation movements for shoulders in my opinion have their place, but I wouldn't do heavy weights with these. Your shoulders already take quite a beating from working back, chest, etc... so it's really not necessary and it will be harder to recover. Most bodybuilders and strength athletes will usually do "fluff" work with shoulder isolation, i.e they will just do pump work with 3-4 sets of 10-15 reps in order to deliver proper nutrients to promote recovery and to get a nice full look. I made the mistake of going heavy with shoulder isolations before and it cost me, so I advise going for volume and frequency as opposed to intensity, but of course everyone is different, and you will find what works best for you.
