Without more context the question is quite open, there is not a single response. It might be the way your fungus naturally grows or it can be due to the culture medium. pH alterations can modify growth pattern. Also depending on the age of the mycelium the consistency will change. If what you need to recover is the mycelium and not what produces into the medium, try to change growth conditions (culture time, pH, agitation if liquid) and also check how you are transferring that fungi between different media (if you are using spores, pieces of mycelium, etc). Without further details, anything could be happening

Generally growth of some fungus strains affected in summer season due to high temperature, try to supplement your culture media with enrichment nutrients and incubate it in suitable temperature

If the mycelium isn't spreading as expected or seems weak, it could be due to:

• Incorrect environmental conditions (temperature, humidity, CO2 levels ,pH ).
• Nutrient deficiency in the substrate.
• Contamination that is inhibiting its growth.