It needs fertilizer at that age.
Okay well it's in soil outdoors obviously. What is the soil LIKE? Is it sandy? Heavy? Dark? Organic looking?
You don't need to use filtered water, just use tap water.
pH does not become a big problem outdoors as much as it does indoors in most situations, however, what is the land around your grow spot like? Mountains, swamp, rocky, ???

To get questions answered you need to be patient; sometimes there will be someone logged in who can help, but not always. With the exception of the regulars in the cultivation section, few people on the site know much about growing, much less troubleshooting.