My LO has some kind of rash that started at the part where the back meets the butt. It's not red but like little bumps (not very visible) and I think it's spreading towards the back. It doesn't look like diaper rash but I'm not sure what it is. Anyone has this issue too?

Yea, could probably diaper rash which I can sometimes see on my baby's skin as well especially when it's hot weather. What I do is whenever we're just at home whole day, I observed that using cloth diaper will help her get rid of it when temp is high. You know diapers have plastic substances that doesn't help in air passage in baby's down part. At the first sign of a diaper rash, try the following steps: Keep the skin dry, and make sure the skin is not in contact with urine and stool. Gently wash the diaper area with warm water and a soft cloth. Before putting on the diaper, make sure the skin's dry already.

It could be heat rash due to diaper. Try to let your lo diaperless or use cloth diaper/napkins. Apply thinly a layer of VCO will help too.