Feels silly, but.... need help with the tub

[Scout19075]

I have these strange yellowy spots (slightly raised, slightly sticky, some of them) on my tub which I think are from a prescription bath oil I was given. Any ideas on how to get them off of my tub? I've been using bog-standard bathroom tub spray cleaner and it's not doing it. I have noticed I can spend five minute thumbnailing the spots and they eventually come off, but I don't have it in me to do that for every single spot....

Thanks!

(BTW, prescription bath oil works a treat and is an excuse for a long soak with a good book!)