Poor latch?

Marissa
So my EBF son is 20 weeks old and has been a very 'juicy baby' from the get go. I've blamed it on my diet and cut out chocolate, coffee, and red sauce which seemed to make a small difference. However, I just got back from a trip to Rome (sans baby) and my husband bottle fed him frozen breast milk the entire time without him spitting up one time 😳 so it's obviously not my diet. It's either a poor latch or a fast let down (or both!) What can you do for a fast letdown and what are some tips to improve his latch? His lips are flanged though so I'm not sure what else to do. Any suggestions would be much appreciated!