If you have a 800 port and adding photos constantly it's probably increasing sales from expanding your portfolio.
This is what I'm assuming. Although some months see decreases or no new sales despite port growth. April is seeing growth commensurate with port growth. That's at least something!
Update: I did check to see my 'profit per image' which should help control for growth. So far PPI is:
SS: already bigger than March & Feb (suggesting better than average sales)
FT: bigger than Feb, 1/3 of March (mixed results, better than Feb, slow compared to March)
123: smaller than Feb but twice March (mixed results but overall good for sales)
DT: bigger than Feb and twice March (better than average sales)
CS: bigger than Feb and approaching March (better than average to average sales)
BS: less than half of Feb, less than 1/2 of March (slow sales)
No point in figuring out IS until PP & subs come in