Best path forward for us

Hello we are currently in quite the time crunch, we went into contract on land and our builders informed us our plan was coming in over budget (it was fine before but after we offered on the land they brought this up). We are tight on time line to get soils, septic engineering, and revised (budget concious) plans developed. Our builders final budget and the plans are all needed before the lender can order a VA Appraisal and get us closed on our land + construction loan. Because of the budget concern we went from ready to go, to scrambling to make a few build plan decisions. Our plans are from: https://www.houseplans.net/floorplans/94000645/mountain-plan-1800-square-feet-3-bedrooms-2-bathrooms This was origanally gonna be a concept that we brought to an architect to build and modify but now due to time concerns we are considering purchasing these plans. My actual question is should we use their service to modify the plans? Or should we get the CAD files of this plan and take them to a local architect? Is that offensive to go that way? Would that actually save time and money to purchase these CAD files? We need to have final plans buttoned up in 4 weeks to stay on track. Is that a reasonable time line?