I would need to know what was used to make up the starter feed. A guarantreed nutritional analysis would be best, but an ingredient list might help with a near guess.
The two most critical nutritional needs for growing birds are Methionine and Lysine - which is why those two appear on US nutritional labels - even though there are plenty of other Amino Acids birds can't produce (or can't produce enough of) on their own. Methinine is needed for building connective tissues - skin and tendons, yes, but also the intestinal tract, which impacts their ability to effectively use what they are fed for much of the remainder of their life - its hard to crawl back from a Met deficiency in early life. Lysine is good for building muscle, particularly breast muscle, and that of course is where most of us "condition score" our birds, and one of the easiest visual clues as to a bird's weight, all other conditions being equal.
Phosphorus is possibly the third most critical, as its needed for bone development at a rate of about 1/2 the calcium they get. Critically, it needs to be a "non phytate", meaning not plant-based, source. Chicken's digestive systems can't effectively absorb phytate phosphorus without help.
Was the feed a local mix??? or do we have a chance at looking it up from here in the US to offer some additional assistance?