Hey buddy, Nice little setup ther pal!
Its very similar to mine, same light, roughly similar space..At first i had foil on my walls, but i got 6m of MYLAR for $25, thats really reflective basically a mirror-tho doesnt absorb light.
Your girls are coming along nicely, for your first grow your doing well.
And being on here is a great way to get help or advice on just about anything,most ppl are happy to help. Iwish my girl had the same spacing during growth as sum of ur girls, i had my light fairly close so she's started off short and bushy but hopefully in week or two she'll be all good. Hope your girls give you some juicy buds when theyre done! Goodluk and Happy HArvesting