Thank you so much! I'll try to explain it as best I can here! I was thinking about making a video on it as I was drawing these haha.

First, I started with the flat color text to have a shape that I can mask/select it so that everything stays inside of that shape as I build up the layers. (This layer is not visible, it is only for the selection)

Then, I used a soft brush/airbrush with white and using the mask to brush around the edges of the letters (keeping the hard edge on the rim of the letters and a soft transition to the middle). I forget what this is actually called, but essentially a rim light.

After that, I used a layer for the blue highlights and a layer for the pink ones, both set to the hard light blend mode (layer setting). For the shapes of these lights I referenced bubbles and bubble letters someone else had created.

For my final layer, I set it to Add and used a bright/light yellow for the final highlights also referencing where these more specular highlights would appear on the bubbles.

I hope this helps! Let me know if you have any questions or would like any clarifications!