Put in only one bag of soil. Is it enough?

Alright so I had to hike pretty far to this spot. I brought 2- 28L bags of Scott's pro blends potting soil, shovel, water and 2 plants. I figured 28 L of good soil would be enough. I dug the hole, 1 ft wide and 1-1/2 to 2 ft deep. This looked really small to me seeing how they produce huge root mass so quick. The exsisting soil was really sandy. The plants were about a 1 ft tall topped with 8 big branches. I'm just thinking that the roots will get much bigger than the hole i dug, and wanted to know Will my plant suffer during flowering stage as the roots make their way into the sandy loam? Will bloom fert help?
For now on I have been using 1 and a half 28L bags and some with 2.

They should be fine since you added the soil to the sandy earth.What type of plants are you growing(sativa or indica)?

im using homemade seeds, napalese grizzly female crossed with a hashplant male. It is an early finishing indica strain, first week of semptember.